Should scentists be allowed to experiment on animals and humans?

I think they shouldn't test on animals because animals don't know what's happening and if they did, they wouldn't choose to go through the pain. But with human, they get paid to do it and are talked through it and treat with respect. My opinion is that animals shouldn't be tested on and human should have a choice. We already have everything we 'need' apart from a cure to cancer, and that may never be discovered, cancer is a natural death! Why kill all those animals to make more products that have already been made and tested by another company? They die in the end and don't get treat the slightest bit!